HU180075B - Method and apparatus for electrochemical processing of mtals - Google Patents

Description

Szemasko Andrei Pavlovies, Gyimayev Nasik Zyatyinovich, Maximov Ivan Vasilyevich, Bezrukov Sergey Viktorovich, Rabinovich Vladimir Borisovich engineer, Ufa, USSR

Process and equipment of metals

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process and apparatus for the precise electrochemical machining of metals and alloys. The process and equipment can be used for various spatial copying processes of workpieces made of hard-to-work materials.

There are several types of electrochemical machining methods created by forced vibration of one electrode. These procedures employ a synchronized voltage pulse applied to the electrodes as they are approached. When the distance between the electrodes is short, the voltage pulse on the vibrating electrode is removed. Voltage supply control significantly reduces machining performance and copy accuracy with minimal electrode spacing.

A method of electrochemical machining using voltage pulses generating synchronized forced oscillation of one electrode is known to control the signal-to-pause ratio in the machining process. Machining starts with small values of the signal-to-pause ratio and increases with increasing values towards the end. The pulse sequence is shifted over time, thus limiting the instantaneous value of the distance between the electrodes fed by the current. In the known process, voltage pulses can be administered both during removal and approximation of the electrodes, but at maximum approximation the electrodes do not receive a voltage pulse.

for electrochemical processing

By adjusting signal-to-syndrome ratios and slipping pulses over time, changes in machining intensity reduce the accuracy of shaping machining, especially when vertical wall surfaces are required.

A characteristic feature of known electrochemical machining processes is that the electrodes have to be energized by voltage pulses at high ranges of space between the electrode faces, which means that at a high average value of the space between the electrode faces, a voltage pulse is introduced. it can produce the surface to be copied only with very limited accuracy15.

During electrochemical machining by forced oscillation of one electrode synchronized with a voltage pulse applied to the electrodes, the distance between the electrodes is controlled by

Author Certificate No. 187,125 (Grade G 05d 3/00) describes the process. In doing so, the electrodes are powered by an additional low-voltage current, and the point of controlling the distance between the electrodes is to utilize the shocks of this current caused by the shorting of the electrodes.

When the spacing between the electrodes is controlled by 30-step changes in the amperage of a low-voltage power source when the workpiece and the tool electrode are touched metallically, there is no

-1180075 possibility to add impulse to working voltage during maximal approximation of electrodes, that is, when the distance between electrodes is minimal, ie possible short circuit between the working surface and the tool electrode! the disorder should be eliminated. The voltage pulses are thus introduced in the known process when the tool electrode is fed or retracted, i.e. at varying values of the space between the electrodes. Given that, in most cases, the vibration amplitude is about 0.2 mm and the operating voltage signal-to-break ratio is between 2 and 3, the electrochemical dissolution process occurs at high average electrode spacing, which adversely affects machining accuracy. This applies especially to the side surfaces of the interior to be machined. If the signal-to-break ratio is increased to 5 to 10 (for example, by significantly increasing the pulse length at operating voltage) to improve machining accuracy, the feed rates will be greatly reduced. In addition, when the electrodes are fed from an additional voltage source, the contact causes strong surface degradation on both the tool electrode and the workpiece. In addition, when the electrodes come into contact, mechanical damage to the tool electrode and workpiece surface can occur, particularly when machining small hollow loads.

Known variations of electrochemical machining methods that use the vibration movement of one electrode synchronized with voltage pulses and known variations of such live working methods to control the size of the electrode can provide only limited machining accuracy, performance, and goodness, particularly with complicated surface designs.

Equipment for electrochemical processing is known to operate on the basis of an analysis of current changes due to various disturbances in the process and short circuits between electrodes.

However, these devices are not suitable for electrochemical machining using pulsed current because the high frequency spectrum of the pulse series suppresses the auxiliary signals of high frequency vibrations in the space between the electrodes due to micro short circuits.

For electrochemical processing, vibration electrode and pulse current devices have also been developed and operate according to a regulating principle: in the absence of mutual contact between electrodes, one of the electrodes is automatically advanced while feed is missing during contact. The impulse voltage that triggers the action can only be introduced when the electrodes are being moved or removed, that is to say, over a large range of space between the electrodes, which significantly diminishes copying accuracy and machining performance.

SUMMARY OF THE INVENTION The present invention relates to a method for electronically machining metals by applying a synchronous oscillation of one of the electrodes by applying a voltage pulse to the electrodes, and to providing a method of demonstrating a minimum space between electrodes during pulse transmission until tool electrode and workpiece are kept to a minimum.

In order to solve this problem, we have developed an electrochemical machining method which uses an electrode which is forced to vibrate synchronously with the voltage pulses applied to the electrodes during the machining process and provides the voltage pulse during the approximation of the electrodes to the minimum distance between the electrodes. and observing the value of the relative resistance as a ratio of the resistance value at the minimum distance between electrodes, then checking the change in the relative resistance value caused by cavitation in the electrolyte when removing the electrodes from each other and comparing the size of the electrode space and the changes in the value of the change. Thus, according to the invention, the distance between the electrodes and the pressure of the electrolyte at the entrance of the space between the electrodes are controlled, while a predetermined change in the relative resistance is kept constant.

The change in relative resistance caused by cavitation when the electrodes are spaced apart is given by periodically adjusting a given range of electrode spacing. The resistance value is always measured and stored. Between measurements, the stored value is compared with the continuously changing actual value of the relative resistance.

For the sake of a change in relative resistance caused by cavitation due to the separation of electrodes from each other! to ensure accurate tracking of the value, measure the second derivative of the relative resistance over time.

When using a power source operating in the current-voltage-reducing section, the change in relative resistance caused by the separation of the electrodes due to cavitation provides a simple and convenient control method in which the ratio of the voltage to the minimum voltage between electrodes is followed by the value of the electrode voltage.

In addition, the relative electrode voltage changes! is also monitored by measuring its second derivative, which is intended to increase sensitivity and to extend the range of control by different shapes of the voltage pulse.

The object of the present invention can also be achieved by providing an electrochemical machining apparatus in which a cavitation transducer is connected to the electrodes according to the invention, the output of which is connected to the input of a processing unit controlling the machining intensity. This control unit includes a first selection and storage unit 2180075 designed for a minimum parameter distance of the cavitation between electrodes. The output of this unit is connected to a first calculator which determines the relative value of the cavitation parameter function. The cavitation output is electrically connected to another input of the first computing unit and to the input of the first selection and storage unit. The output of the first computing unit is connected to an input of a second selection and storage unit formed to a relative value of the cavitation parameter function and an input of a comparator unit for comparing the current function value of the cavitation parameter to a predetermined value. The other input of the comparison unit is connected to the output of the second selection and storage unit. The output of the comparator unit is connected to a locking circuit, the output of which is also the output of a control unit that determines the machining intensity and is connected to a setting mechanism. The control inputs of the first selection and storage unit for the minimum value of the distance between the electrodes of the cavitation parameter and of the second selection and storage unit formed for the relative value of the function of the cavitation parameter, and the control input of the locking circuit are connected to a simultaneous control unit.

Preferably, the processing intensity control unit is connected to a second order differentiation unit having an input to the cavitation transmitter and an output connected to another input of the first computing unit which provides a relative value of the cavitation parameter function.

The cavitation transmitter can be designed as a voltage transmitter.

The cavitation transducer may also be configured as a voltage and current transducer whose outputs are connected to a second calculator for determining the resistance between the electrodes and its output is the cavitation transducer output.

The process and apparatus of the present invention facilitate various three-dimensional copying operations of workpieces made of hard-to-machinable materials, providing high machining accuracy, performance and superior quality, both in the production of complex surface products and in the production of large numbers of workpieces of the same size.

The invention will now be described in more detail with reference to specific embodiments, based on the accompanying drawings. In the drawing it is

Fig. 1 is a diagram of an apparatus for carrying out the process of the present invention for electrochemical machining, a

Fig. 2 is a graph showing the changes in the machining process parameters during the vibration movement of a tool relative to the workpiece surface,

Figure 3 is a graph of the relative parameter change caused by cavitation when removing the tool electrode from the workpiece surface, depending on the minimum value of the space between the electrodes;

Fig. 4 is a block diagram of the electrochemical processing apparatus of the present invention

Fig. 5 is a functional diagram of the electrochemical processing apparatus according to the invention, a

Figure 6 shows an embodiment of the apparatus according to the invention comprising a second order differentiation unit, a

Figure 7 shows an embodiment of a cavitation transducer, a

Figure 8 is a schematic of another cavitation transducer, a

Fig. 9 is a graph of changes in the relative value of the clock electrode and its second derivative with a large minimum distance between the electrodes;

Figure 10 is a graph of changes in the relative value of electrode voltage and its second derivative with a small value of the minimum distance between the electrodes;

Figure 11 shows the change in relative resistance of the electrode space and the second derivative of the relative resistance over time with a large value of the minimum distance between electrodes,

Figure 12 shows the change in relative resistance of the electrode space and the second derivative of the relative resistance over time, with a small value of the minimum distance between electrodes,

Figure 13 is an explanatory diagram of the operation of the first selection and storage unit for the value of the cavitation parameter with a minimum value of electrode spacing,

Fig. 14 is a diagram of the operation of the second selection and storage unit for the relative value of the cavitation parameter function.

The process according to the invention is as follows. From a suitable power supply 1 (Fig. 1), voltage pulses U are applied to the tool electrode 2 used as a tool and another electrode representing the workpiece 3. The frequency of the voltage pulses U is synchronized in the direction indicated by the arrows so that the voltage pulse operates until the tool electrode 2 and the workpiece 3 are at a minimum distance, i.e. the tool electrode 2 is in the lower position.

During electrochemical machining, an electrolyte having a pressure P _x flows through the inlet S of the electrode between the tool electrode 2 and the workpiece 3. The electrodes are converging at high speeds with vibratory motion created by 4 motors. The workpiece 3 is mounted on a table 5 moving at a speed v in the direction of the tool 2. Rapid approximation of the tool 2 and the workpiece 3 results in _a pressure P _s (Fig. 2) in the electrolyte filling the space S between the electrodes. The vapor and gas bubbles present in the electrolyte and formed during the electrochemical process are compressed by the hydrodynamic pressure P _s and dissolved in the electrolyte. As a result, during the anodic dissolution of the workpiece surface 3 (Fig. 1), the probability of permeation of the S-electrode space due to these conditions is significantly reduced 3, which is also due to the absence of vapor and gas bubbles (Fig. 2). As a result, the distance between the electrodes can be reduced, which contributes significantly to the precision, performance and quality of machining.

When the tool electrode 2 is rapidly removed from the workpiece 3 (Fig. 1), the hydrodynamic pressure P (Fig. 2) drops abruptly. In this case, the vapor and gas bubbles 6 dissolved in the electrolyte are re-formed intensively in the space S between the electrodes, i.e., due to the reduction of the pressure P ₆ , cavitation is created in the electrolyte filling the space S between the electrodes. As a result, the resistance R, which characterizes the space S between the electrodes, is significantly increased (Figure 2, Section A). As the distance between the electrodes increases further, fresh electrolyte flows into the space S, which is washed away and the resistance R begins to decrease over time (Figure 2, Section B). Thus, when the tool 2 is removed from the workpiece 3, the resistance R first increases with respect to section A and then decreases with respect to section B, i.e. a local extreme change in the resistance R is observed.

The intensity of the formation of vapor and gas bubbles 6 during electrochemical machining due to cavitation due to the removal of the tool electrode 2 is dependent on the minimum distance S " _ln characterizing the space S between the electrodes (Fig. 2) and the amount of electrolyte flowing through space 8. This can also be described as the smaller the Sp-.S distance between the electrodes S (Fig. 3a), the smaller the electrolyte flow in this space and the faster the electrolyte is enriched in the space between the electrodes. and gas bubbles. Thus, when the tool electrode 2 is moved away from the surface of the workpiece 3, the number of vapor and gas bubbles 6 in the space S between the electrodes increases avalanche-like. As a result, the resistance R of the electrode space S increases significantly at the moment of displacement (Fig. 3b is the section A _{4 for the} distance S ₄ ).

If the electrochemical processing is performed at a high minimum distance between the electrodes, S ₄ (Fig. 3a), the electrochemical processes will be less intense and the electrolyte will be slightly enriched in the space S between the electrodes with vapor and gas bubbles. Therefore, the formation of the vapor and gas bubbles 6 when the tool electrode 2 is retracted is formed only in small quantities. Therefore, the change in resistance R due to cavitation is barely observed (Fig. 3a, section Aj), and will be much smaller than that of section A ₄ .

The intensity of cavitation resulting from the removal of the tool electrode 2 from the surface of the workpiece 3 is thus affected by the magnitude of the distance S between the electrodes and the flow of the electrolyte.

There is a clear relationship between the degree of cavitation intensity and the minimum distance S _mIn between the electrodes S at a given entry pressure P, which can be used to control the machining process.

As the resilient motion of the tool 2 is removed by oscillatory movement, the resistance R between the electrodes increases dramatically with the advancement of cavitation, so that the resistance R of the space S between the electrodes is changed by controlling the machining process by cavitation in the electrolyte! value can be used.

The relative resistance of the space between the electrodes is determined by dividing the value of space S between the electrode resistance of the resistance value between the electrodes for a minimum S _mln distance. When controlling according to the relative parameter, the surface to be machined, the electrolyte temperature, the conductivity, etc. effect is excluded.

Before starting the machining, the electrode 2 and the workpiece 3, which vibrate relative to one another, are brought into contact with one another by turning it counterclockwise, and then removed at a _minimum spacing S _min between the electrodes (Fig. 2). Then, an actuating pulse U is applied to the electrodes (Fig. 1) and an electrolyte is introduced into the space S between the electrodes at a pressure P ₄ , whereby the machining begins.

Since there is a clear relationship between the minimum _{span Sm} (Figure 1) and the magnitude of the relative resistance of the cavity, the maximum value of the change in cavity relative to the electrode S is stored, and this stored value is hereinafter referred to as a value which transmits the machining intensity transversely, determined primarily by the set size S of the electrode space.

Continuous changes in the relative resistance of the electrode space created by cavitation, if different from the given value, are used to change the feed rate (v) and pressure (P,), where, when the relative resistance value exceeds the specified value, P increasing the pressure and decreasing the feed rate v. If the value of the relative resistance is below the specified value, the feed rate v is increased.

Adjustment of a predetermined distance of _{Sm to} the electrode space, simultaneously measuring the relative resistance of the electrode space, and storing the measured value periodically during the intense cavitation development, are performed at intervals of several times every 10 minutes. This is because the temperature and electrical conductivity of both the surface to be machined and the electrolyte vary relatively slowly in the machining process.

Figure 3b shows that the local extrema (A ₄ , Α », A ₃ , A ₄ ) of the relative resistance of the electrode S increases with the reduction of the minimum distance S ',' between the electrodes.

If the electrodes are removed, the cavitation phenomena cause deformation (distortion) of the relative resistance curve, leading to the appearance of local extremes on the curve. Since the value of the local extreme is below the value of the relative resistance for larger distances between the electrodes, comparing the instantaneous value of the relative resistance with the

180073 is difficult and therefore comparisons need only be made up to the moment when the most intense cavitation develops.

Therefore, the second derivative of the relative resistances of the space between the electrodes should be used to control the process.

The value of the second derivative of a function is proportional to the curvature of the function at a given point, and therefore, since the intensity of cavitation appears as the local extreme of the relative resistance curve, where the degree of curvature increases with the peak of the local extreme as the intensity of cavitation increases. 3c and then, after double differentiation, modify the degree of cavitation to change the local extreme of the curve as seen in Figure 3c. This curve shows the second derivative of the relative resistance between the electrodes and shows that the pulses Aj ... Aj, which represent the amplitudes of the global extremes, increase with the change in the minimum distance S "" between the electrodes (Figure 2).

When using the power supply 1 operating in the curve of the current-voltage curve (Figure 1), the changes in relative electrode voltage generated by cavitation in the electrolyte when the electrodes are pulled apart are used to control the process.

Relative voltage is defined as the ratio of the voltage across the electrode voltage to the minimum distance _SmI between the electrodes. Relative parameter control eliminates changes in power supply voltage 1, electrolyte or surface temperature to be machined, etc. .

It is known that a voltage proportional to the resistance is present in the consumer when powered from a power source. This means that the U electrode voltage pulse varies with the intensity of the cavitation. Fig. 3d shows that as the minimum distance R ',' between the electrodes S decreases (Fig. 2), the value of the local extremities of the curve increases with the change of the relative electrode voltage.

The change in the local extrema of the curve describing the changes in the relative voltage determining the intensity of the cavitation is determined on the basis of the value of the second derivative of the relative electrode voltage.

Figure 3e shows that with the decrease of the minimum distance S _n , _ln characteristic of the S space between the electrodes, the amplitudes C _{1 to} C _{4 of} the global extremes increase on the second derivative of the relative voltage curve.

.The electrochemical machining system comprises a cavitation transducer 7 connected to the tool electrode 2 and the workpiece 3 (Fig. 4). The output of the cavitation transmitter 7 is connected to one of the inputs 8 of the control unit 9. The control unit 9 determines the machining intensity. The tool electrode 2 is connected to the output rails 1 of the workpiece 3 pulsed power supply.

The control unit 9 comprises a first selection and storage unit 10 which stores a valid cavitation parameter at a minimum distance of S _mil between the electrodes S. The first selection and storage unit 10 is connected to the input of the first calculator 12 which determines the relative value of the function of the cavitation parameter (Fig. 4). The input 13 of the first calculator 12 and the input 14 of the first selection and storage unit 10 are connected to the output of the cavitation transducer 7. The output of the first calculator 12 is connected to the input 13 of the second selection and storage unit. The second selection and storage unit 16 stores the relative value of the function of the cavitation parameters and is led to the input 17 of the comparison unit 18. The comparison unit 18 compares the current value of a function of the cavitation parameter with a predetermined value, and its input 19 is connected to the output of the second selection and storage unit 16. The output of the comparator unit 18 is connected to the input 20 of the locking circuit 21, while the output of the locking unit 21, as the output of the control unit 0, provides a processing intensity control signal to an adjusting mechanism 22.

The control inputs 23, 24, and 25,26 of the first selection and storage units 10 and 16, respectively, and the control input 27 of the locking circuit 21 are connected to a time control unit 28.

The first selection and storage unit 10 (Fig. 5) stores a cavitation parameter representative of a minimum distance of S _ml between electrodes. A basic element is a storage capacitor 29, one arm of which is grounded and the other arm 30 is coupled via a MOSFET transistor 30 to the input 14 of the first selection and storage unit 10 and the input 11 of the first calculator 12. The storage capacitor 29 comprises a resistor 31 connected to one of the corners of the storage capacitor discharge circuit with the ungrounded armature of the storage capacitor 29. The other corner of the resistor 31 is coupled to ground through a MOSFET transistor 32. The control inputs of the MOSFET transistors 30 and 32 are connected to the control inputs 23 and 24 of the first selection and storage unit 10.

A first calculator divider 12 for determining the relative value of a function of the cavitation parameter, comprising 33 operational amplifiers. The inverting input and output of the operational amplifier 33 are coupled via a capacitor 34, while the inverting input is coupled via a resistor 35 to a function generator 36 and through an output of the operational amplifier 38 via a resistor 37. The output of the operational amplifier 38 is connected to the input 17 of the comparator unit 18. The inverting input of the operational amplifier 38 is connected to the input 14 of the first calculator 12 and via the resistor 39 to the output of the operational amplifier 38. The function generator 36 provides two multiples of the variable and connects one of its inputs to the output of the operation amplifier 33 and the other to the input 11 of the first calculator. Operational amplifiers 33 and 38 are guided to ground by non-inverting inputs.

In the second selection and storage unit 16, the relative value of the function of the cavitation parameter is 5

It is stored in a storage capacitor 511, one arm of which is grounded and the other arm is connected via MOSFET resistors 41 to input 15 of second selection and storage unit 16 and input 19 of comparator unit 18. The storage capacitor 40 includes a resistor 42 coupled to one of the corners of the storage capacitor discharge circuit to the unearthed armature of the storage capacitor 40. The other corner of the resistor 42 is grounded through a MOSFER transistor 43. The control inputs 10 of the MOSFET transistors 41 and 43 are connected to the control inputs 25 and 26 of the second selection and storage unit 16, respectively.

The comparator unit 18, which processes the current relative value of a function of the cavitation parameter and a predetermined value, comprises a differential operation amplifier 44, the output of which is also the output of the comparator unit 18, which is led to the input 20 of the closing circuit 21. The inverting input of the differential operation amplifier 44 is coupled to the output of the operational amplifier 45, the inverting input of which is connected to the input of the comparator unit 18 and to the output of the operational amplifier 45 via a resistor 46. The non-inverting input of the differential operation amplifier 44 is connected to the output of the operational amplifier 47, which is connected via a resistor 48 to the inverting input of the operational amplifier 47, while the inverting input is connected to the 19 input of the comparator unit 18. The non-inverting outputs of the operational amplifiers 45 and 47 are grounded. 30

The locking circuit 21 comprises an AND gate 49, one of which inputs is formed by the input 20 of the locking circuit 21 and the other input is connected via an inverter 50 to the control input 27 of the locking circuit 21. The output of the AND gate 49 is also the output of the working intensity control unit 9 and is connected to the adjusting mechanism 22.

Second order differentiation is performed by 51 second order differentiation units (Figure 6). This includes operation amplifiers 52 and 53, which in turn are tightly coupled to each other by resistors 54 and 55 connected to their inverting inputs.

The output of the operation amplifier 53 is connected to the output 13 of the secondary differential unit 51 and the first calculator 12, while the inverter input 45 is connected to the output of the operational amplifier 52 via a differential capacitor 56. The converting input of the operational amplifier 52 is coupled via a differential capacitor 57 to the input 8 of the control unit 9 and to the input 14 of the first selection and storage unit 10. Operational amplifiers 52 and 53 are connected to ground by non-inverting inputs.

The cavitation transmitter 7 (Fig. 7) can be configured as a voltage transmitter. It is based on a counter-current operation amplifier 58 55 whose inverting input is output to its output via a resistor 59. The output of the operational amplifier 58 is connected to the input 8 of the control unit 9, while its inverting input is connected to the center of the potentiometer 60. One corner of the potentiometer 60 60 is grounded and the other corner is connected to the negative potential tool electrode 2.

In another embodiment of the cavitation transducer 7 (Fig. 8), a second calculator 65 is used to determine the resistance 61, the output of which is also the output of the cavitation transducer 7 and is connected to the input 8 of the control unit. The input 62 of the second calculator 61 is connected to a voltage transmitter 63 whose input is connected to the negative potential tool electrode 2. The input 64 of the second calculator 61 is connected to the output 65 of the current transducer.

The voltage transducer 63 includes an operational amplifier 66 which is connected to the clenitem via a resistor 67 via its non-inverting input. The output of the operation amplifier 66 is connected to the input 62 of the second calculator 61 and its non-inverting input is directed to the center of the potentiometer 68. One corner of the potentiometer 68 is grounded while the other has a negative potential tool 2 connected to an electrode. The inverting input of the operational amplifier 66 is grounded.

The current transducer 65 comprises an operational amplifier 69 which is coupled to a resistor 70 via a non-inverting input via a resistor 70. The output of the operational amplifier 69 is connected to the input 64 of the second calculator 61, while its non-inverting input is connected to the center of the potentiometer 71. The corners of the potentiometer 71 are connected in parallel with the resistor 73 and lead to the output coil of the transformer 72. The inverting input of the operational amplifier 69 and one of the corners of the potentiometer 71 are grounded,

The second calculator 61 is based on an operation amplifier 74 having an inverting input with capacitive feedback generated by an integrating capacitor 75. The output of the operation amplifier 74 is also an output of the cavitation transducer 7. The output of the function generator 77 is connected to the inverting input of the operation amplifier 74 via a summing resistor 76 and one corner of the resistor 78, while the other corner of the resistor 78 is connected to the input 62 of the second calculator 61. One of the inputs of the function generator 77 is coupled to the output of the operational amplifier 74.

Figure 9 shows the following:

- change in the distance between the electrodes (S) over time (Figure 1), - the reference value of the relative electrode voltage, - the change in the relative electrode voltage, - the second derivative of the relative electrode voltage, - the reference of the second derivative of the relative electrode voltage.

Figure 10 shows the following:

- change of the distance S between the electrodes over time (Figure 1),

S5 - reference level of the relative electrode voltage, - curve of the change in the relative voltage value, - the change of the second derivative of the relative electrode voltage, - the reference level of the second derivative of the relative electrode voltage,

89, 90 - output signal of the closing circuit 21 (Fig. 5),

Indicated in Figure 10 correspond to the curves of the electrodes 613 co-p ^ ,, Zotti minimum distance that is less than the distance of FIG 0. p _'mln distance.

Figure 11 shows the following:

- time variation of the distance S between the electrodes (Fig. 2), - voltage variation curve, - variation in current between electrodes (Fig. 1), - variation in the relative resistance of the electrode space, reference level for the relative resistance of the space between electrodes (Fig. 1), - second derivative of the relative resistance of the space between electrodes as a function of time (Fig. 1), - a predefined reference level for the second derivative of relative space between electrodes (Fig. 1).

Figure 12 shows:

- time-varying curve of the distance S between the electrodes (Fig. 1),

100 - current in the space between the electrodes (Figure 1),

101 - curve of relative clearance of electrode space (Figure 1),

102 - reference level of the relative resistance of the electrode space ie (Figure 1),

103 - second derivative of the relative resistance of the space between the electrodes as a function of time (Figure 1),

104 - predefined reference level of the second derivative of the relative resistance,

105, 106 - output signal of lock circuit 21 (fig. 5).

figure).

Figure 13 shows the following:

107 - time change of the distance S between the electrodes (Figure 1),

108 - clektródfeszültség the temporal change in which U _mln minimum S between the electrodes _ml "voltage value corresponding to the distance (Figure 2);

109 - a control signal provided to the control input 24 of the first selection and storage unit 10 (Fig. 5),

110 - the control signal provided to the control input 23 of the first selection and storage unit 10,

111 - Voltage of storage capacitor 29 of first selection and storage unit 10 (Fig. 5)

112 - Control signal for input 27 of locking circuit 21 (Fig. 5).

Figure 14 shows:

113 - change of the distance between electrodes S over time (Figure 1),

114 - the change in the relative electrode voltage over time, where U "" is the maximum value of the relative voltage,

115 - the second selection and storage unit 16 (Fig. 5).

control signal given to 26 controller inputs,

116 - the second selection and storage unit 16 (Fig. 5).

control signal for 25 control inputs,

117 - the second 16 selection and storage units (Fig. 5).

The voltage applied to its 40 storage capacitors,

118 - control signal provided to input 27 of lock circuit 21.

Prior to machining, the tool electrode 2 and workpiece 3 are approached in contact with no movement in counter-current until they are contacted and then adjusted to a minimum distance of S _mil between the electrodes (Fig. 2). A voltage pulse U (Figure 1) is then applied to the electrodes when the pressure of the electrolyte in the space S between the electrodes is Pt. This is when the electrochemical machining begins.

Since the degree of cavitation intensity in the electrolyte during the removal of the tool electrode 2 by oscillatory movement, at a predetermined pressure P, the electrolyte is clearly dependent on the minimum distance S "," between the electrodes (Fig. 2). 2), the value of a selected parameter is measured which unambiguously determines the cavitation intensity corresponding to the set minimum distance between the electrodes.

To exclude the effects of a change in the output voltage of the power supply 1, the electrolyte temperature, and the surface temperature of the workpiece 3, the signal provided by the cavitation transducer 7 is applied to the input of the first calculator 12, whereby divided by parameters corresponding to a minimum spacing of S _ml between electrodes.

The value of the cavitation parameter is determined using the first selection and storage unit 10 (Fig. 4) with a minimum distance S _mi between the electrodes. It is connected to the output 14 of the unit to the output of the cavitation transducer 7 and forms an analog storage unit which, at specified intervals, checks the actual value of the cavitation parameter at a minimum distance of S _mil between the electrodes. The output signal of the first selection and storage unit 10 is applied to the input 11 of the first calculation unit 12, where the output of the first calculation unit 12 transmits a signal proportional to the relative value of the function of the cavitation parameter. Since the value of this signal is clearly related to the minimum distance _Sm set between the electrodes prior to machining, this signal is stored in the second selection and storage unit 16 and used as a reference value over a specified machining period. The second selection and storage unit 16 forms an analog storage device.

Thus, at the start of electrochemical machining, the value of the cation parameter function, which corresponds to the given minimum distance _Sm in the space S between the electrodes, must be calculated and stored.

A signal is provided to the input 27 of the locking circuit 21 (FIG. 4) from the timing control unit 28, which closes the signal path to the adjusting mechanism 22 to prevent the entry of a faulty signal. The faulty signal may occur during the storage cycle when the first selection and storage units 10 and 16 are switched on. The closing mark is maintained after the cycle is completed.

To the end of the initial machining phase.

Even after storing the values of the required processing intensities in the first selection and storage units 10 and 16, the comparator 18 connected to the output of the first calculator 12 by its input 17 and the output of the second selection and storage unit 16 by its input 19 compares the current value of the function of the cavitation parameter with the corresponding signal to the reference value.

If the relative actual value 10 of the function of the cavitation parameter remains below the reference values, the comparator 18 generates a signal by which the adjusting mechanism 22 increases the feed rate v of the tool electrode 2 (Fig. 1).

If the situation is reversed, the comparator unit 18 to 15 (Figure 4) generates a signal based on which the adjusting mechanism 22 reduces the feed rate v and the space between the electrodes in the inlet pressure P _x increases.

The relative value of the minimum distance between the electrodes and the cavitation parameter, which clearly determines the conditions between the electrodes, are periodically measured and stored at intervals of 5 to 19 minutes, or even less frequently, taking into account the number of 2 electrodes in the workpiece 3. low penetration rate.

Measurement of the cavitation parameter value and storage of the value at a minimum distance S _mi between the electrodes is generally performed after 5 to 10 30 electrode movements.

The timing diagram underlying the operation of the control unit 9 is implemented by the time control unit 28, such that by the control signals 109, 110, 112 shown in FIG. 13 and the 115 and 116,118 signals shown in FIG. actuating the second selection and storage unit 16 (Fig. 4) and the locking circuit 21.

The mode of operation of each unit and circuit 40 of the control unit 9 (Fig. 5) for determining the machining intensity will now be described in detail.

The cavitation transmitter 7 provides an output signal corresponding to the value of the cavitation parameter, which is supplied to the input of the first selection and storage unit 10. In this unit 45, by briefly opening the MOSFET transistor 30, the storage capacitor 29 is charged at a minimum distance of S _ml between electrodes (FIG. 2). This capacitor stores a voltage corresponding to the minimum electrode distance 50 of the cavitation parameter during several vibration periods of the tool electrode 2.

The capacitor 29 discharges through the resistor 31 when transistor 32 is switched on briefly. 55

The process of selecting and storing the cavitation parameter in FIG. 13 is illustrated in FIGS. 107, 108, 109, 110,

With reference to curves 111 and 112, the electrode voltage is used as the cavitation parameter. 60

The output signals of the cavitation transmitter 7 (Fig. 5) and the output signals of the first selection and storage unit 10 are applied to the inputs 13 and 11 of the first calculator 12. The first calculator 12 determines the relative value of the function of the cavitation parameter and forms a divisor 65 8 which implements the function Z = X / Y into a differential equation Z '= —k, ZY = X, Z (0) = 0. . Variable X corresponds to the input 13 of the first calculator 12, variable Y corresponds to the input 11 of the first calculator 12, variable Z corresponds to the output of the first calculator 12.

The integration and summing tasks are performed by a capacitive feedback 33 operational amplifier with 35 cs 37 summing resistors.

The operational amplifier 38 inverts the variable X. The function generator 36 multiplies the variables Y and Z and can be generated in any standard analog computer circuitry, such as a logarithmic amplifier. This method can be used to create the entire calculator.

The signal corresponding to the relative value assigned to the function of the cavitation parameter is output from the output of the first calculator 12 to the second selection and storage unit 16, which operates in an analogous manner to the first selection and storage unit 10 described above. In Fig. 14, his work is illustrated by the curves 113, 114, 115, 116, 117, and 118 when the cavitation parameter is selected as the electrode voltage.

Unlike the first selection and storage unit 10 (Fig. 5), the storage capacitor 40 is charged until the change in resistance R in the space between the electrodes becomes maximal due to cavitation.

The relative time value of the cavitation parameter is compared with the reference value using the comparator unit 18 (Figure 5). This unit is based on a differentiating operation amplifier 44 which receives input from the outputs of the first calculator 12 and the second selection and storage unit 16 via the operational amplifiers 45, 47.

By generating the comparative signals as a positive potential at the output of the comparator unit 18, the signal passes through the AND gate 49 to the tuning mechanism 22. This signal reaches the adjusting mechanism 22 only when the closing signal provided by the timing control unit 28 is missing and supplied to the input 27 of the closing circuit 21, i.e. the inverter 50.

Since the cavitation development during the vibratory movement of the tool electrode 2 is accompanied by a sharp increase in the resistance S between the electrodes, the change in the resistance between the electrodes caused by cavitation is useful in the present invention.

The cavitation transducer 7 (Fig. 8) operates on the basis of measuring the resistance between the electrodes.

Measurements are made on the basis of current and voltage measurements, for which 63 voltage transmitters and 65 current transmitters provide the appropriate signal (Figure 3). Their output signals are directed to the inputs 62 and 64 of the second calculator 61 constituting the resistor and divider.

The voltage transmitter 63 is based on a potentiometer 68 whose voltage is transmitted from the center via the non-inverting input of the operational amplifier 66 to the input 62 of the second calculator 61.

The current transducer 65 functions as a transformer 72

-817 having an output voltage through the potentiometer 71 and the non-inverting input of the operational amplifier 69 to the input 64 of the second calculator 61.

The second calculator 61, which determines the value of the resistance, corresponds to the first 12 calculator described above (Fig. 4) in both construction and operation. At its output, it generates a signal proportional to the actual resistance value of the space between the electrodes.

The curves 91, 92, 93, 94 and 95 in Fig. 11 show the change in voltage, current, and relative resistance characteristic of the space between the electrodes with a minimum value of p ' _mil between the electrodes at which cavitation cannot occur. If the minimum distance between the electrodes is reduced to p _mil , when cavitation may occur (curves 98, 99, 100, 101, 102, and 105 in Figure 12), when the tool electrode 2 is fed, a change in curve 101 is observed in relative resistance caused by the change. Compared to curve 94 of FIG. 9, comparator unit 18 (FIG. 5) until the time of maximum cavitation development is based on a reference value stored in second selection and storage unit 16 (curve 102, FIG. 12) at the beginning of the last electrode distance adjustment cycle, was fixed before machining, it produces a relative value.

The shape of the curves 99 and 100 (Fig. 12) shows a rigid current-voltage characteristic when the power source 1 is used.

If the power source 1 is used in a decreasing branch of the current-voltage characteristic, a voltage transmitter (Fig. 7) based on a potentiometer 60 may be used as a cavitation transmitter. The voltage is applied via the operational amplifier 58 to the input 8 of the control unit 9 which determines the machining intensity. It is known that the voltage of the current flowing through the consumer when feeding consumers is proportional to the resistance. This means that the shape of the voltage pulse U on the electrodes, i.e. the tool electrode 2 and the workpiece 3, changes strongly depending on the intensity of the cavitation.

When comparing the curves (Fig. 9, Fig. 81, Fig. 10, 86, Fig. 9, 79 and Fig. 84) with different values of the minimum distance between the electrodes, the curve 86 shows the peak of the relative voltage, which is due to a change in cavitation. Compared to the reference level (FIG. 10 85), the output of the locking circuit 21 (FIG. 5) shows a signal 89 for controlling the adjusting mechanism 22.

The distortion of the curves of the relative resistance between the electrodes and the relative electrode voltage is evident during the development of the cavitation process as a local extreme on the right side of the curves, which corresponds to retraction of the tool electrode 2 (Fig. . Determining the local extreme with the amplitude method is difficult because it would be necessary to release the comparator unit at the time of maximum cavitation intensity.

The accuracy of the measurement of the cavitation intensity is improved by measuring the value of the local extreme of the electrode voltage versus electrode field resistance curves, such that the second unit 51 has a second order differential between input 8 and input 13 of the first calculator 12. activating a differentiator unit, which supplies a voltage or resistance signal from the output of the cavitation transducer 7, which differentiates the signal through a series of differentiated operation amplifiers 52, 53 and then transmits it to the input of the first calculator 12 for calculating the relative signal value.

The value of the second derivative of the function is proportional to the curvature of the function at a given point, and since the cavitation intensity is a local extreme on the curve of relative voltage or relative resistance, the degree of curvature of the local extreme peak increases with increasing cavitation intensity. By deriving a derivative based on relative voltage or relative resistance, the amplitude can readily be compared to a reference value in the comparator unit 18 to provide a signal for controlling the adjusting mechanism 22.

Figures 9 and 10 show the second derivative of relative voltage for two characteristic values of the minimum electrode distance (curves 82, 83, 87, 88 and 90).

Figures 11 (curves 88, 89) and 12 (curves 97, 95, 96) show the second derivative of the relative resistance for the two characteristic values of the electrode distance (curves 96, 97,103, 104 and 105).

Due to cavitation, the distortion on the curve of the second derivative exhibits a global extreme when the tool electrode 2 is offset. This allows the intensity of the cavitation to be determined simply and conveniently and, consequently, to maintain the machining intensity with high accuracy.

The process and apparatus of the present invention provide very high precision (0.02 mm) in the shape of electrochemical machining of complex hollow surfaces, in various copy-space operations, when difficult to process but electrically conductive material is required. The finished workpiece has an excellent surface quality and a machining power of 0.8 mm / min.

The high accuracy of the shape of the surfaces to be machined practically eliminates the problem of sizing and correction of the tool electrode 2. The tool electrode 2 can be used to produce a large number of workpieces, provided that their deviation does not exceed 0.02 mm.

This is achieved by moving the tool electrode 2 in the machining process in a vibrational movement synchronized with voltage pulses in the feed direction.

The properties of the electrolyte used, the optimum vibration period of the tool electrode 2 and the adaptive control system in the process ensure that the process is conveniently located at a distance of 0.02 to 0.05 mm

-919 is possible, without damaging the tool electrode and workpiece surface, if the electrolyte is introduced into the space between the electrodes at the required pressure P.

Claims (9)

CLAIMS 1. A method of electrochemically treating metals by applying a synchronized voltage pulse to one of a plurality of electrodes moved relative to one another in an electrolyte, characterized in that, during the approximation of the electrodes, the and comparing the value of the relative resistance as a function of the time-varying value of the characteristic resistance to the minimum distance between electrodes, then checking the change in the relative resistance value caused by cavitation in the electrolyte when the electrodes are spaced apart, and regulate the pressure of the electrolyte at its input with a constant change in the required change in relative resistance k. 2. The method of claim 1, wherein the change in the relative resistance of the electrode space required when the electrodes are removed and caused by cavitation in the electrolyte is periodically adjusted by the amount of electrode distance required in the machining process. and wherein the change value used to compare the change in relative resistance 35 to the given initial value is always measured and stored in the space between the electrodes. 3. A method according to claim 1, wherein the change in the relative resistance of the electrode space 40 caused by cavitation in the electrolyte when the electrodes are removed is measured by measuring a second derivative of the relative resistance. 25 4. The method of claim 1, wherein the feeding is performed from a power source operating in a decreasing portion of the current-voltage characteristic of the relative electrode voltage and is caused by the cavitation in the electrolyte when the electrodes are spaced apart. change is monitored by the ratio of the continuous voltage value to the minimum distance between electrodes. 5. The method of claim 4, wherein the change in relative electrode voltage is monitored by measuring a second derivative of the relative voltage over time. 6. Electrochemical processing equipment a 1-5. Method according to claims for carrying out, characterized in that the connector kavitációadója (7) are electrodes, the output of which is connected to one input of a machining intensity control unit (9) (8), wherein the control unit (9) belonging to the minimum distance (S _mln) between electrodes kavitációparaméterre comprising a first selection and storage unit (10), a control input (23, 24) of the first selection and storage unit (10) for a periodic control unit (28), an output to an input (12) of a first calculator (12) for determining the relative value of the cavitation parameter. 11) connected, the input of the first selection and storage unit (10) being led to the other input (13) of the first calculator (12), the output of the first calculator (12) being configured for a second value adapted to the relative value of the cavitation parameter change connected to the input (16) of the asteroid and storage unit and to one of the inputs (17) of the comparator relative to the current relative value and a predetermined reference value for changing the cavitation parameter, the other input (19) of the comparator (18) to the second selection and storage unit (16) is connected, the control inputs (25, 26) of the second selection and storage unit (16) are connected to a timing control unit (28), the output of the comparator (18) is connected to a closing switch (21) and forming the output of the control unit (9) and connected to an adjusting mechanism (22), while the control input (27) of the closing switch (21) is led to the output of the time control unit (28). An embodiment of the apparatus of claim 6, wherein the control unit (9) comprises a second order differentiator (51) having an input to the cavitation transmitter (7) and an output to the other input (13) of the first calculator (12). 8. The device according to claim 6 or 7, characterized in that the cavitation transmitter (7) is a voltage transmitter. An embodiment of the apparatus according to claim 6 or 7, characterized in that the cavitation transducer (7) comprises a voltage transducer (63) and a current transducer (65), the outputs of which are connected to the inputs of a second calculator (61) and the output of the second calculator (61) is an output of the cavitation transducer (7).